There are 2 approaches to this kind of setup:
You have a shared home directory over nfs. In which case you use the AutoFS method to mount the home dir on access under /home (like you did with putting /home in auto.master)
You have no shared home, and want a homedir for the user on each server he logins to. In this case you need pam_mkhomedir to create the directory upon first login.
It seems that you mixed both methods, by requesting autofs to mount /home/ and create a homedir on login.
You should choose one method and stick to it. If you want the homedir to be automounted, you'll have to create it with the user so it is available to him throught NFS.
You could try and merge the 2 methods by making /home automounted. Since that means you'll have to run AutoFS on /, perhaps it is better having /home/users automounted. Then you can have pam_mkhomedir create a homedir at /home/users/